Secondary battery pack and authentication method

ABSTRACT

An authenticator ( 5, 11 ) is compatible with a plurality of authentication systems to authenticate an external device connected with a connection terminal (OUT, ID), and the authenticator executes authentication processes by the plurality of authentication systems in order, and permits transfer of electric power between the external device and a secondary battery part ( 1 ) when any one of authentication processes is successful.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2013/067317 filed Jun. 25, 2013, claiming priority based onJapanese Patent Application No. 2012-204150 filed Sep. 18, 2012, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a secondary battery pack executing anauthentication process of an external device.

BACKGROUND ART

When an irregular external device is used as an external device thattransmits or receives electric power to/from a secondary battery,current that does not comply with the specifications of the secondarybattery may flow into the secondary battery, resulting in a possibilitythat the secondary battery will fail. Therefore, a technique ofpreventing a failure of the secondary battery is used in which anauthentication process of a secondary battery pack including a secondarybattery and an external device is executed.

For example, Patent Literature 1 discloses an information processer thatauthenticates a secondary battery pack. The information processerexecutes a first authentication process that uses a first authenticationID stored in the secondary battery pack and a second authenticationprocess that uses second and third authentication IDs stored in thesecondary battery pack, and when both the authentication processes aresuccessful, charge of the secondary battery pack is performed.

CITATION LIST Patent Literature

Patent literature 1

JP2009-195014A

SUMMARY OF INVENTION Technical Problem

In the technique disclosed by Patent Literature 1, since theauthentication process is executed by using the authentication ID, anexternal device that can be used as a battery charger is used only forthe secondary battery pack, and thus, even if there is a general batterycharger that complies with specifications, the battery charger cannot beused and this lead to a problem of high cost.

Regarding this point, instead of executing an authentication processusing an authentication ID, a possible authentication process is anauthentication process executed based on a value of current flowing intothe secondary battery. Specifically, when the value of the currentflowing into the secondary battery falls within a predetermined rangethat meets the specifications of the secondary battery, a successfulauthentication process allows the general battery charger compliant withthe specifications of the secondary battery to be used.

However, in a case where the secondary battery pack is connected to anexternal device such as an electric power-assisted bicycle andregenerative current is supplied from the external device to thesecondary battery pack, the value of the regenerative current variesdepending on the situation, and thus, the value of the regenerativecurrent does not necessarily fall within a predetermined current range.Therefore, if an authentication process is executed based on the valueof current flowing into a secondary battery, determination may be madethat an external device is an irregular battery charge which wouldprevent charging with regenerative current.

An object of the present invention is to provide a secondary batterypack that allows for usage of a general battery charger compliant withspecifications thereof while allowing for charging with regenerativecurrent, and an authentication method.

Solution to Problem

A secondary battery pack of the present invention includes: a secondarybattery part; a connection terminal connectable with an external devicethat transmits or receives electric power to/from the secondary batterypart; and an authenticator that is compatible with a plurality ofauthentication systems to authenticate the external device connectedwith the connection terminal, the authenticator configured to executeauthentication processes by the plurality of authentication systems inorder and permitting transfer of electric power between the externaldevice and the secondary battery part when any one of the authenticationprocesses is successful.

An authentication method of the present invention is an authenticationmethod performed in a secondary battery pack including a secondarybattery part and a connection terminal connectable with an externaldevice that transmits or receives electric power to/from the secondarybattery, the secondary battery pack being compatible with a plurality ofauthentication systems to authenticate the external device connectedwith the connection terminal, the method comprising: executingauthentication processes by the plurality of authentication systems inorder; and permitting transfer of electric power between the externaldevice and the secondary battery part when any one of the authenticationprocesses is successful.

Advantageous Effects of Invention

According to the present invention, it is possible to use a generalbattery charger compliant with the specifications while allowing forcharging with regenerative current.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a secondary batterypack of a first exemplary embodiment.

FIG. 2 is a flowchart explaining an operation of the secondary batterypack of the first exemplary embodiment.

FIG. 3 is a diagram illustrating a configuration of a secondary batterypack of a second exemplary embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, description will be given of exemplary embodiments withreference to the drawings. In the following descriptions, componentswith the same functions are denoted by the same reference character, anddescription thereof is omitted in some cases.

FIG. 1 is a diagram illustrating a configuration of a secondary batterypack of a first exemplary embodiment. In FIG. 1, secondary battery pack50 includes secondary battery part 1, discharge FET (field effecttransistor) 2, charge FET 3, sense resistor 4, protective IC 5, IDauthentication resistors 6 to 8, switches 9 and 10, MCU (micro controlunit) 11 and a grounding terminal GND.

Secondary battery pack 50 further includes, as a connection terminalconnectable with an external device, output terminal OUT, transmittingterminal TX, receiving terminal RX, authentication terminal ID, andauthentication cancellation terminal ID-C. Output terminal OUT andauthentication terminal ID are used for transmitting or receivingelectric power to/from the external device, and transmitting terminalTX, receiving terminal RX and the authentication cancellation terminalare used for communicating with the external device.

The external device is, for example, a battery charger supplyingelectric power to secondary battery pack 50 or a load device operatingwith electric power from secondary battery pack 50. In the followingdescription, the external device is a battery charger. Also, the batterycharger includes a device supplying electric power by regenerativecurrent to secondary battery pack 50, such as an electric power-assistedbicycle.

Secondary battery part 1 is configured by a rechargeable secondarybattery cell. Further, a positive electrode of secondary battery part 1is connected to output terminal OUT, and a negative electrode ofsecondary battery part 1 is connected to authentication terminal ID andgrounding terminal GND.

In the present exemplary embodiment, secondary battery part 1 has aconfiguration in which a plurality of secondary battery cells 1A arerespectively connected in series. However, secondary battery part 1 maybe configured by a single secondary battery cell, or may have aconfiguration in which a plurality of secondary batteries arerespectively connected in parallel or in matrix. Also, the type ofsecondary battery cell 1A is not particularly limited, but secondarybattery cell 1A is, for example, a lithium ion secondary battery cell.

Discharge FET 2, which is a switch controlling discharge current outputfrom secondary battery part 1, is disposed between secondary batterypart 1 and output terminal OUT. Charge FET 3, which is a switchcontrolling charge current supplied to secondary battery part 1, isdisposed between secondary battery part 1 and output terminal OUT. Inthe present exemplary embodiment, charge FET 3 is disposed betweendischarge FET 2 and output terminal OUT. Further, discharge FET 2 andcharge FET 3 are a p-type FET.

Sense resistor 4, which is a resistor for sensing charging current anddischarging current of secondary battery part 1, is disposed betweensecondary battery part 1 and authentication terminal ID. In thefollowing description, charging current and discharging current arecorrectively referred to as charging/discharging current, in some cases.

Protective IC 5 measures a resistance voltage which is a voltage acrossthe ends of sense resistor 4, and senses charging/discharging currentflowing into secondary battery part 1 based on the resistance voltage.Protective IC 5 notifies MCU 11 of the value of the sensedcharging/discharging current. Also, protective IC 5 senses a batteryvoltage which is the voltage across the ends of each secondary batterycell 1A.

The protective IC determines whether an abnormality such as overcharge,overdischarge and overcurrent to secondary battery part 1 occurs basedon the sensed charging/discharging current and battery voltage, and theprotective IC uses discharge FET 2 and charge FET 3 to protect secondarybattery part 1 when the abnormality occurs.

For example, when at least any one of the respective battery voltages isequal to or more than the overcharge threshold, protective IC 5determines that overcharge to secondary battery cell 1A has occurred,and turns off charge FET 3 to protect secondary battery part 1 fromovercharge.

Moreover, when at least any one of the respective battery voltages isequal to or less than the overdischarge threshold, protective IC 5determines that overdischarge of secondary battery part 1 has occurred,and turns off discharge FET 2 to protect secondary battery part 1 fromoverdischarge.

Furthermore, when charging/discharging current is equal to or more thanthe overcurrent threshold, protective IC 5 determines that overcurrentto secondary battery part 1 has occurred, and turns off discharge FET 2to protect secondary battery part 1 from overcurrent.

ID authentication resistors 6 to 8 and switches 9 and 10 are circuitsfor altering the resistance value viewed from authentication terminalID.

One end of ID authentication resistor 6 is connected to authenticationterminal ID, while the other end is connected to one of the ends of IDauthentication resistors 7 and 8 and switch 9. The other end of IDauthentication resistor 8 is connected to one end of switch 10. Theother ends of ID authentication resistor 7 and switches 9 and 10 areconnected to sense resistor 4. In the present exemplary embodiment,switches 9 and 10 are configured by an n-type FET.

MCU 11 switches on/off of switches 9 and 10 to switch the resistancevalue viewed from authentication terminal ID (more specifically, aresistance value across authentication terminal ID and sense resistor4).

At that time, when MCU 11 turns off both switches 9 and 10, theresistance value viewed from authentication terminal ID is a seriesresistance value of ID authentication resistors 6 and 7. When MCU 11turns off switch 9 and turns on switch 10, the resistance value viewedfrom authentication terminal ID is a series resistance value of IDauthentication resistor 6 and a parallel resistance value of IDauthentication resistor 7 and ID authentication resistor 8. When MCU 11turns on switch 9, irrespective of whether switch 10 is turned on orturned off, the resistance value viewed from authentication terminal IDis the resistance value of ID authentication resistor 6.

As described so far, in the present exemplary embodiment, MCU 11 canswitch on/off of switches 9 and 10 to make the resistance value viewedfrom authentication terminal ID switchable in three ways.

MCU 11 assigns a state in which switch 9 is on so that it is in acharging stop state in which charging of secondary battery part 1 isstopped, assigns a state in which switch 9 is off and switch 10 is on sothat they are in a normal charge state in which secondary battery part 1is charged by normal current, and assigns a state in which switches 9and 10 are off so that they are in to a pre-charge state in whichsecondary battery part 1 is charged by pre-charge current that issmaller than the normal current, and thus, the charging state ofsecondary battery part 1 is managed. In the charging stop state, MCU 11turns off charge FET 3 via protective IC 5, while in the normal chargestate and the pre-charge state, MCU 11 turns on charge FET 3 viaprotective IC 5.

MCU 11 functions as an authenticator that is compatible with a pluralityof authentication systems to authenticating an external device connectedwith the connection terminal, executes authentication processesperformed by the respective authentication systems in order, and permitstransfer of electric power between the external device and secondarybattery part 1 when any one of the plurality of the authenticationsystems is successful. The authentication time period required forcompleting the determination of whether an authentication process is ornot possible is different among the respective authentication systems,and the authenticator executes the plurality of authentication systemsin order starting from an authentication system having the shortestauthentication time period.

Next, description will be given of a specific example of authenticationprocessing by MCU 11 to authenticate an external device.

In the following description, an authentication system includes a firstauthentication system that executes an authentication process forauthenticating an external device based on an external signal input fromthe external device, and a second authentication system that executes anauthentication process for authenticating the external device based on avalue of charging current supplied from the external device to secondarybattery part 1. Also, the authentication time period of the firstauthentication system is shorter than the authentication time period ofthe second authentication system, and therefore, MCU 11 first executesthe authentication process of the first authentication system, andsecond executes the authentication process of the second authenticationsystem.

The external signal is a signal for executing an authentication processof an external device. In the present exemplary embodiment, the externaldevice inputs an ID cancellation signal indicating whether the secondauthentication system is to be executed, as an external signal, to MCU11 via an ID cancellation terminal ID-C. Also, the ID cancellationsignal indicates execution of the authentication process of the secondauthentication system in the case of an H level, while indicating noexecution of the second authentication system in a case of an L level.

First, at the timing to start charging secondary battery part 1 in thecharging stop state, MCU 11 determines whether an external signal inputfrom the external device is the H level or the L level, as theauthentication process of the first authentication system.

If the ID cancellation signal is the L level, MCU 11 determines that theauthentication process of the first authentication system is successful,and permits the external device to charge secondary battery part 1.

On the other hand, if the ID cancellation signal is the H level, MCU 11determines that the authentication process of the first authenticationsystem is failed, and executes an authentication process of the secondauthentication system.

Specifically, MCU 11 turns off switches 9 and 10 and turns off chargeFET 3 via protective IC 5 to transit to the pre-charge state. Then, MCU11 determines whether the value of charging/discharging current outputfrom protective IC 5 falls within a set value range, which is apredetermined current value range, as the second authentication system.The set value range is a range of the value of current that complieswith specifications of secondary battery part 1 in the pre-charge state,which is, for example, a range equal to or lower than 0.1 ItA.

If the value of the charging/discharging current falls within the setvalue range, MCU 11 determines that the authentication process of thesecond authentication system is successful, and permits the externaldevice to charge secondary battery part 1. On the other hand, if thevalue of charging/discharging current does not fall within the set valuerange, MCU 11 determines that the authentication process by the secondauthentication system has failed, and transits to the charging stopstate to stop the external device from charging secondary battery part1.

Next, operation of secondary battery pack 50 will be described.

FIG. 2 is a flowchart explaining an example of the operation ofsecondary battery pack 50. In the operation described below, anauthentication system includes the first authentication system and thesecond authentication system, as in the aforementioned specific example.

At the charging start timing to start charging by the external devicewhen the external device has been connected to secondary battery pack50, MCU 11 determines whether an ID cancellation signal that was inputto authentication cancellation terminal ID-C is the H level or not (stepS201).

If the ID cancellation signal is the H level, MCU 11 determines that thefirst authentication process is failed, and turns off both switches 9and 10 and turns on charge FET 3 via protective IC 5 to transit to thepre-charge state (step S202).

When transiting to the pre-charge state, MCU 11 checks a value of thecharging current output from protective IC 5, and determines whether ornot the value of the charging current falls within the set value range(step S203).

If the ID cancellation signal is the L level at step S201 and the valueof the charging current falls within the set value range at step S203,MCU 11 determines that the authentication process is successful, andturns off switch 9 and turns on switch 10 to transit to the normalcharge state (step S204). At that time, if the charge FET is off (if theID cancellation signal is the L level at step S201), MCU 11 turns oncharge FET 3 via protective IC 5.

Accordingly, secondary battery part 1 is charged. Thereafter, MCU 11determines whether it is at the charging end timing to end charging ofsecondary battery part 1 (step S205). For example, if protective IC 5senses, based on the battery voltage or the charging/dischargingcurrent, that secondary battery part 1 is fully-charged or thatsecondary battery part 1 is abnormal, protective IC 5 notifies MCU 11 ofan end signal indicating that effect. Then, if MCU 11 receives the endsignal, MCU 11 determines that it is at the charging end timing. If MCU11 does not receive the end signal, MCU 11 determines that it is not atthe charging end timing.

If the value of the charging current does not fall within the setcurrent value range at step S203, and if the charging end timing issensed at step S205, MCU 11 turns on switch 9 and turns off the chargeFET via protective IC 5 to transit to the charging stop state (stepS206).

Thereafter, MCU 11 determines whether it has been at the charging starttiming or not (step S207). For example, if protective IC 5 senses, basedon the battery voltage or the charging/discharging current, that thefully-charged state of secondary battery part 1 ends or that theabnormality of secondary battery part 1 is eliminated, protective IC 5notifies MCU 11 of a start signal indicating that effect. Then, if MCU11 receives the start signal, MCU 11 determines that it is at thecharging start timing. If MCU 11 does not receive the start signal, MCU11 determines that it is not at the charging start timing.

If it is at the charging start timing, MCU 11 returns to step S201. Ifit is not at the charging start timing, MCU 11 returns to step S206.

As described so far, according to the present exemplary embodiment, whenauthentication processes by a plurality of authentication systems areexecuted in order and when any one of the authentication processes issuccessful, transfer of electric power between the external device andsecondary battery part 1 is permitted. Accordingly, if any one of anauthentication process that allows for charging with regenerativecurrent and an authentication process that allows for usage of a generalbattery charger compliant with the specifications is successful,transfer of electric power between the external device and secondarybattery part 1 is permitted, and thus, it is possible to use the generalbattery charger that complies with the specifications, while allowingfor charging with regenerative current.

Furthermore, in the present exemplary embodiment, the authenticationprocesses of the authentication systems are executed in order startingfrom the authentication system with the shortest authentication timeperiod, and thus, it is possible to reduce the time period required forthe authentication process.

Moreover, as the authentication system, the first authentication systembased on an external signal input from the external device is executed,and thus, if the battery charger which supplies regenerative current tosecondary battery part 1 is only provided with a function for outputtingan external signal, it is possible to easily execute an authenticationprocess to allow for charging with the regenerative current.

Furthermore, as the authentication system, the second authenticationsystem, in which an authentication process for the external device basedon the value of current supplied to secondary battery part 1 isexecuted, and thus, it is possible to execute an authentication processto allow for usage of a general battery charger that complies with thespecifications.

Next, a second exemplary embodiment will be described.

In the first exemplary embodiment, MCU 11 executes the authenticationprocesses by the plurality of authentication systems in order. In thepresent exemplary embodiment, MCU 11 executes an authentication processof an authentication system selected from among a plurality ofauthentication systems. If the executed authentication process issuccessful, MCU 11 permits transfer of electric power between theexternal device and secondary battery part 1. Note that theauthentication system in the present exemplary embodiment is, forexample, the first and second authentication systems, which areexemplified in the first exemplary embodiment.

FIG. 3 is a diagram illustrating a configuration of secondary batterypack 50A of the present exemplary embodiment. Secondary battery pack 50Aillustrated in FIG. 3 includes selection signal terminal SE in additionto the configuration of secondary battery pack 50 illustrated in FIG. 1.

A selection signal to select any authentication systems from among theplurality of authentication systems is input to selection signalterminal SE. For example, secondary battery pack 50A is provided with aswitch for selecting any authentication systems from among the pluralityof authentication systems, and when a user switches the switch, aselection signal is input from the switch to selection signal terminalSE.

MCU 11 selects any authentication systems from among the plurality ofauthentication systems, according to the selection signal input toselection signal terminal SE, and executes an authentication process ofthe selected authentication system. Then, if the executed authenticationprocess is successful, MCU 11 permits transfer of electric power betweenthe external device and secondary battery part 1.

It is also possible that secondary battery pack 50A is provided with aconnection terminal that connects with the external device for eachauthentication system, MCU 11 senses the connection terminal connectedwith the external device, and selects any authentication systems fromamong the plurality of authentication systems according to the sensedconnection terminal.

According to the present exemplary embodiment, it is necessary to selectan authentication system, but it is possible to use a general batterycharger compliant with the specifications, while allowing for chargingwith regenerative current, as in the first exemplary embodiment.

In the aforementioned exemplary embodiments, the illustratedconfigurations are only an example, and the present invention is notlimited to the configurations.

For example, if the ID cancellation signal is the L level, the IDcancellation signal may indicate execution of the second authenticationsystem, while if the ID cancellation signal is the H level, the IDcancellation signal may indicate non-execution of the secondauthentication system.

The present application claims the priority of Japanese PatentApplication No. 2012-204150 filed on Sep. 18, 2012, the entiredisclosure of which is incorporated herein.

REFERENCE SIGN LIST

-   1 secondary battery part-   1A secondary battery cell-   2 discharge FET-   3 charge FET-   4 sense resistor-   5 protective IC-   6 to 8 ID authentication resistor-   9, 10 switch-   11 MCU-   50, 50A secondary battery pack

What is claimed is:
 1. A secondary battery pack comprising: a secondarybattery; a connection terminal connectable to an external device thattransmits electric power to or receives the electric power from saidsecondary battery; and an authenticator compatible with a plurality ofauthentication systems to authenticate the external device connected tosaid connection terminal, the authenticator is configured to executeauthentication processes of the plurality of authentication systems inorder and to permit transfer of the electric power between the externaldevice and said secondary battery in response to any one of theauthentication processes being successful, wherein the external deviceis a battery charger that charges said secondary battery, and a firstone of the plurality for authentication systems comprises a first one ofthe authentication processes of the external device and is executedbased on a value of current supplied from the external device to saidsecondary battery.
 2. The secondary battery pack according to claim 1,wherein an authentication time period required for completingdetermination of whether an authentication process is possible isdifferent among the authentication systems.
 3. The secondary batterypack according to claim 2, wherein the authenticator implements theplurality of authentication systems in order, starting from anauthentication system comprising a shortest authentication time period.4. The secondary battery pack according to claim 1, wherein any one ofthe plurality of authentication systems is a first authentication systemin which an authentication process for the external device is executedbased on an external signal for executing the authentication process forthe external device, the external signal being input by the externaldevice.
 5. The secondary battery pack according to claim 4, wherein theauthenticator first implements the first authentication system.
 6. Thesecondary battery pack according to claim 5, wherein a second one of theplurality of authentication systems comprises a second one of theauthentication processes for the external device and is executed basedon a second value of the current supplied from the external device tosaid secondary battery, and the authenticator secondly implements thesecond authentication system.
 7. The secondary battery pack according toclaim 6, wherein, in the second one of the plurality of authenticationsystems, the second one of the authentication processes for the externaldevice is executed based on whether the second value of the currentfalls within a predetermined current value range.
 8. The secondarybattery pack according to claim 4, wherein, in the first authenticationsystem, the authentication process for the external device is executedbased on whether the external signal is the H level or the L level. 9.An authentication method performed in a secondary battery packcomprising a secondary battery and a connection terminal connectable toan external device that transmits electric power to or receives theelectric power from the secondary battery, the secondary battery packbeing compatible with a plurality of authentication systems toauthenticate the external device connected to the connection terminal,the method comprising: executing authentication processes by theplurality of authentication systems in order; and permitting transfer ofthe electric power between the external device and the secondary batteryin response to any one of the authentication processes being successful,wherein the external device is a battery charger that charges saidsecondary battery, and a first one of the plurality for authenticationsystems comprises a first one of the authentication processes of theexternal device and is executed based on a value of current suppliedfrom the external device to said secondary battery.